The invention relates to rotors for electric motors and, specifically, to rotor shafts and how they are attached to such rotors.
In prior art methods of attaching a rotor shaft to a rotor stack to build a rotor for an electric motor, a solid round rotor shaft is manufactured. Laminations are also manufactured, a hole is stamped through the center of each lamination, and the laminations are then attached to each other in a face-to-face orientation to create a rotor stack having a central bore formed by the holes in the laminations. The rotor shaft is inserted in the bore through the entire length of the rotor stack. Commonly, the rotor stack is heated and the shaft is cold when the shaft is inserted. When the parts cool, a pressure bond is formed between the rotor stack and the rotor shaft, thus yielding a rotor in which the rotor stack is mechanically attached to the rotor shaft.
Using such a prior art method of attaching a rotor shaft to a rotor stack, scrap is generated when each rotor lamination is stamped with a hole for the shaft. In addition, the shaft hole in the rotor stack creates magnetic losses that lower motor efficiency.
The invention provides a rotor in which shaft portions are welded directly to the ends of a rotor stack, preferably by friction welding.
The invention solves both the scrap and efficiency problems by eliminating the need for the shaft hole in the rotor, thus providing a rotor in which each lamination of the rotor stack has an unstamped, solid center, and the rotor stack preferably has therein no other bores. As a result, no scrap is generated and motor efficiency is improved. In addition, the amount of shaft material needed is also reduced because the shaft does not extend through the rotor stack.
Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims, and drawings.